Ammunition target discriminator

ABSTRACT

In a high explosive projectile which is designed to function on impact and which includes an inertially activated detonator power supply, that improvement which comprises an impact nose plug threaded into the projectile aligned with and spaced from but proximate the power supply. The plug material and the mating threads jointly providing a functioning or non-functioning of the ammunition for selected targets dependent on the shear characteristics thereof. Thus, the system can be made to function for certain targets and be non-functional for other light targets such as thin structures, tree branches, bushes, etc.

United States Patent [191 Schwartz et al.

[ AMMUNITION TARGET DISCRIMINATOR [75] Inventors: Jacob Schwartz, Rockaway; George Rosner, Dover, both of NJ.

[73] Assignee: The United States of America as represented by the Secretary of the Army, Washington, D.C.

221 Filed: Apr. 22, 1971 211 Appl. No.: 136,465

[56] References Cited UNITED STATES PATENTS 11/1967 Bedall 102/73 R 12/1967 Bedall 102/73 R TD DETONATOR June 12, 1973 Primary Examiner-Benjamin A. Borchelt Assistant Examiner-J. V. Doramus Att0rneyl'larry M. Saragovitz, Herbert Berl,

Edward J. Kelly and Ernest F. Weinberger [57] ABSTRACT In a high explosive projectile which is designed to function on impact and which includes an inertially activated detonator power supply, that improvement which comprises an impact nose plug threaded into the projectile aligned with and spaced from but proximate the power supply, The plug material and the mating threads jointly providing a functioning or nonfunctioning of the ammunition for selected targets dependent on the shear characteristics thereof. Thus, the system can be made to function for certain targets and be non-funcional for other light targets such as thin structures, tree branches, bushes, etc.

3 Claims, 1 Drawing Figure PAIENIEDJWZW 3373.2?5

INVENTORS, GEORGE ROSNER -TO DETON ATOR AMMUNITION TARGET DISCRIMINATOR The invention described herein may be manufactured, used and licensed by or for the Government for governmental purposes without the payment to us of any royalty thereon.

BACKGROUND OF THE INVENTION The present invention relates to impact detonation ammunition and more particularly pertains to an impact target discriminator for ammunition wherein the projectile will detonate only on impact with selected strength targets and will be non-functional for relatively light targets.

In the field of 152 MM ammunition target discrimination, it has been general practice to employ inertially activated detonators such as those wherein a weighted sphere moves forward on deceleration, such as impact, and closes a spring type switch arrangement that in turn activates the detonator. The spring switch and the inertial sphere have a certain spring constant such that, by adjusting the same, the detonator might be activated under certain conditions. These units were designed with a minimum spring constant such that the detonator would be activated or function on graze. This however, introduced another problem, namely, the ammunition would detonate in the air (air bursts) due to deceleration as well as on striking soft targets such as branches and brush. On the other hand, if the spring constant were increased the projectile would detonate only on impact with relatively hard targets and penetrate targets such as thin wooden building walls without detonation. Such devices have proved to be unsatisfactory in'that they can not be fabricated to provide absolute target discrimination without the inherent limitation of air bursts.

SUMMARY OF THE INVENTION The general purpose of this invention is to provide an ammunition target discriminator that has all the advantages of similarly employed prior art devices and has none of the above described disadvantages. To attain this, the present invention provides a plug disposed at the impact face of the projectile nose and is frangibly disposed therein as by selectably shearable threads. The thread dimensions as well as the material composition of the projectile nose and plug determine the target discrimination factor when the plug is employed with and spaced from an inertial fuze or detonator power supply. Thus, the detonation is dependent on both target type impact and projectile deceleration.

An object of the present invention is to provide a target discriminator for a high explosive projectile which is simple, inexpensive and which may be used in conjunction with an inertial fuze system to detonate on impact with selected targets-and to non-functionally penetrate light targets.

Another object is to provide a target discriminator which is not subject to air bursts and yet operational for graze impact. Y

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood'by reference to the following detailed description when considered in connection with the accompanying-drawing wherein the single FIGURE thereof is a cross-sectional view of an embodiment of the invention made in accordance with the principle of this invention.

DESCRIPTION OF A PREFERRED EMBODIMENT In the illustrated embodiment of the invention, the forward end or windshield of the projectile 10 is provided with a central axial aperture within which is disposed a portion of the fuze system, as for example a control power supply 11. The inertial supply here, provides electrical energy to an aft located detonator upon deceleration or projectile impact to activate the same. In simplified form the supply operates as follows: disposed behind the inertial mass sphere 12 is a metallic disc 13 which is supported thereat by abutting metallic ram 14 that in turn is held fast by annular insulator 15 bearing against metallic disc switch 16. Disposed and supported between the ram 14 and the insulator 15 is an impact switch member 17 which is essentially a thin metallic disc having a central portion in the shape of an H deleted so as to provide a pair of integral spring like fingers l8 and 19. These fingers under the action of the sphere moving forward will be brought into direct, intimate contact with the disc 16 which is in electrical contact with the supply housing. This latter contact results in connecting the output of an electrical source, such as a piezoid, to the detonator. Thus it is clear that the sphere will move forward under the decelerating forces imposed on the projectile and will be restrained only by the spring action of the switch member 17. Essentially, the spring constant thereof and the mass of the sphere determine the type of target on which detonation will and will not occur and is generally completely independent of any other components. In evaluating the functioning of the system, targets constructed of plywood are employed with a requirement that the system function for plywood of one inch thickness and remain nontainly, where the switch system functions for graze impact but is not satisfactory for target discrimination.

This problem has been solved by providing another element to independently function the switch, which element, will be translated under the action of forces in excess of specific values. The element is essentially of the frangibly held type as for example, a plug 20 which is threaded into the nose aperture forward of the supply 1 1. The thread size and pitch and the material composition of the projectile windshield determine the shear force necessary to shear or free the plug permitting it to translate rearwardly and impact the disc 16, crush it against the impact switch member 17, thereby activating the detonator in the same manner as the action of the sphere upon deceleration. In fabrication the windshield cap or nose can be counterbored to provide a relatively thin web of metal in the nose equivalent in shear strength to the threaded section of the plug although the two need not be of the same material. It has been found that for a windshield fabricated of aluminum alloy ASTM designation 7075 and a plug of aluminum alloy 2017 or 2024 with a thread designated as 025-20 UNEF-ZA provided satisfactory results and the ability to discriminate thicknesses of plywood. The power supply is fixedly supported so that it can not move and the rear end surface 21 of the plug is spaced from the face 22 of the supply to prevent any vibratory or other shock forces from being transmitted thereto when impacting targets of lesser than the military requirements and causing activation thereof. This spacing insures by its isolation positive action and eliminates any unreliability occasioned by intermittent or vibratory motion on the part of the plug. Essentially two critical features, namely, the conrolled shear and the space or air gap intermediate the fuze system (supply) and the frangible element (plug) provice an operational device which meets the necessary specifications of functional performance.

It should be understood, of course, that the foregoing disclosure relates to only a preferred embodiment of the invention and that numerous modifications or alterations may be made therein without departing from the spirit and the scope of the invention as set forth in the appended claims.

We claim:

1. A target discriminator for a high explosive projectile having a fuze system activated by deceleration and disposed proximate the forward end of said projectile, said discriminator comprising:

an element releasably and longitudinally supported in said projectile forward of but proximate said fuze system and having a face thereof defining at least a portion of the forward impact surface of said projectile, aligned and coextensive therewith, said element being spaced and isolated from said fuze system and provided with external threads and, said projectile forward end formed with a longitudinal aperture having internal threads, said element being threadable therein to constitute a shearable combination.

2. The discriminator according to claim 1 wherein said element is spaced from the forward end of said fuze system to provide isolation.

. 3. The discriminator according to claim 2 wherein said fuze system is of the inertial type. 

1. A target discriminator for a high explosive projectile having a fuze system activated by deceleration and disposed proximate the forward end of said projectile, said discriminator comprising: an element releasably and longitudinally supported in said projectile forward of but proximate said fuze system and having a face thereof defining at least a portion of the forward impact surface of said projectile, aligned and coextensive therewith, said element being spaced and isolated from said fuze system and provided with external threads and, said projectile forward end formed with a longitudinal aperture having internal threads, said element being threadable therein to constitute a shearable combination.
 2. The discriminator according to claim 1 wherein said element is spaced from the forward end of said fuze system to provide isolation.
 3. The discriminator according to claim 2 wherein said fuze system is of the inertial type. 